1. Field of the Invention
This invention relates to a bubbler ampoule and assembly for containment and shipping of toxic and corrosive liquid chemicals; and more particularly to a bubbler ampoule and assembly for containment of ultra high purity liquid chemicals that can develop relatively high vapor pressures.
2. Brief Description of the Art
Many manufacturing processes utilize high-purity liquid chemicals which are entrained in a carrier gas for such procedures as semiconductor water doping, vapor deposition, water surface etching and cleaning, and the like. These high-purity liquid chemicals are shipped in and dispensed from high purity containers commonly known as "bubblers", due to the nature of the dispensing process. The bubbler assemblies are commonly formed from high purity quartz glass, glass, silicon, and non-reactive polymers, among other suitable materials. U.S. Pat. No. 4,140,735 Schumacher; U.S. Pat. No. 4,851,821 Howard et al.; and U.S. Pat. No. 4,886,178 Graf, all describe typical liquid chemical bubbler assemblies and systems that use liquid chemical bubbler assemblies.
Liquid chemical bubbler assemblies are used in the following manner in the production of semiconductor wafers or other components. The liquid chemical is disposed in a sealed container, i.e., the bubbler assembly, which includes an ampoule and inlet and outlet valves. The ampoule is provided with an inlet neck that is connected to a hollow dip tube portion for admitting a carrier gas to the ampoule, which dip tube portion extends below the surface of the chemical in the ampoule. The ampoule also includes an outlet neck from which a gas stream that has been saturated with the liquid chemical is fed to the wafer processing station. The carrier gas stream is passed through the inlet neck and enters the liquid chemical below the surface of the chemical, where it bubbles its way to the top of the liquid chemical. The bubbling action creates an upper area in the bubbler assembly that is saturated with the chemical entrained in the carrier gas. The saturated solution is then drawn out of the bubbler assembly through the outlet neck and fed into a high temperature processing zone, or the like, where the chemical is exposed to the semiconductor wafers or other components to be treated. The inlet and outlet necks of the ampoule are fitted with valves that are manipulated to control the release of the chemical from the ampoule. The ampoule and the valves combine to form the bubbler assembly.
The particular liquid chemicals which are used in the aforesaid systems include, among others: 1,1,1-trichloroethane; 1,2 dichloroethylene; phosphorus oxychloride; boron tribromide; and the like. Some of these chemicals develop high vapor pressures while in use, and high-pressure vessels are needed for containment. This is particularly the case with the more corrosive chemicals used for etching and cleaning semiconductor wafers. One problem associated with the dispensing of the aforesaid chemicals relates to the strength of the bubbler assemblies which house the chemicals, and their ability to withstand relatively high degrees of pressurization without breaking. This is a particular problem when the ampoules must be formed from high purity quartz glass due to the nature of the chemicals they will be containing. Typical flat-bottomed ampoules which are made from high purity quartz glass are capable of being pressurized to pressures in the range of about fifteen psi to about twenty psi before bursting. It would be highly desirable to have a liquid chemical bubbler ampoule and assembly which could withstand higher pressures without bursting.